1) Since the check is done for freedom of movement in freezing conditions i would use 0° C as well, as does my company. And of course whenever deicing is needed, after deicing is finished, but usually the temperature is below 0° by then.
2) Per SOP we do, just before reading the preflight checklist. Newer Airplanes have an AUTO-Position instead of off, they start to heat up on their own whenever an engine is running.
3) Ref speeds are determined by the EFB performance program. Therefore we don't have a fixed number of speeds to memorize. If the runway is both contaminated and has degraded braking action we have to calculate both values and take the more limiting one.